Geology Ch 7

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A body of gneiss is subjected to heat and forms a melt. Later the melt cools and crystallizes to form a(n) : . a., metamorphic rock b., igneous rock c., sedimentary

b. igneous rock

Metamorphism brings changes in mineral arrangement and the texture of rocks, but it never leads to new mineral assemblages. a., true b., false

b. false

A buried body of aragonitic limestone is recrystallized at low temperatures and pressures, producing calcite; this is an example of : . a..diagenesis b..erosion c..metamorphism d..weathering

a. diagenesis

A buried body of shale is subjected to differential stress at temperatures greater than 200C, causing clay minerals to grow in preferred orientation and producing slate. This is an example of : . a..diagenesis b..erosion c..metamorphism d..weathering

c. metamorphism

At the surface, potassium feldspar reacts with water to form clay; this is an example of : . a..diagenesis b..erosion c..metamorphism d..weathering

d. weathering

Clay minerals within a buried body of shale are recrystallized at 400C and high pressure to form mica, producing a rock called phyllite; this is an example of : . a..diagenesis b..erosion c..metamorphism d..weathering

c. metamorphism

Metamorphism may be induced by : . a..contact with a hot pluton b..contact with hot groundwater c..heat and pressure associated with deep burial d..all of the above

All metamorphic rocks are formed within a fairly narrow range of temperatures, approximately 400 to 600C. a..true b..false

b. false

A primary difference between phyllite and schist is : . a..schist contains mica, but phyllite contains only clay b..phyllite contains mica, but schist contains only clay c..mica crystals within schist are larger than those within phyllite d..mica crystals within phyllite are larger than those within schist

Marble and quartzite are nonfoliated rocks because : . a..they are never found beneath fault zones or collisional mountain ranges b..both are dominated by minerals that produce equant grains c..both are dominated by minerals with crystalline structures that cannot be dissolved d..dynamothermal metamorphism can break down the structures of their constituent minerals, but neither of these minerals is stable in that metamorphic environment

b. both are dominated by minerals that produce equant grains

Two common metamorphic rocks that typically lack foliation are : . a..slate and phyllite b..gneiss and migmatite c..quartzite and marble d..schist and metaconglomerate

c. quartzite and marble

Compared to low-grade metamorphic rocks, high-grade rocks : . a..always contain more quartz and feldspar b..are produced closer to the surface, high in the stratigraphic column c..are produced at greater temperatures and pressures d..are produced at cooler temperatures, but greater pressures

c. are produced at greater temperatures and pressures

A mineral within a metamorphic rock that can be used to provide a narrow constraint on the temperature and pressure of formation of the rock is termed a(n) : . a..thermineral b..index mineral c..mafic mineral d..halide mineral

Phyllite would most likely be found : . a..in an aureole around a cooled igneous intrusion b..at the eroding base of an ancient collisional mountain range c..at depth within the mid-ocean ridge system d..within a meteorite impact crater

Rocks resulting from thermal (contact) metamorphism will not possess : . a..a new mineral assemblage distinct from that found prior to intrusion b..larger crystals than those characterizing the country rock prior to intrusion c..foliation d..silicate minerals

c. foliation

Regional metamorphism : . a..takes place at cool temperatures and low pressure b..takes place at cool temperatures but high pressure c..is another name for thermal metamorphism d..is another name for dynamothermal metamorphism

Within a single mountain range, : . a..only low-grade metamorphic rocks are likely to be found b..only high-grade metamorphic rocks are likely to be found c..it is possible to find a variety of metamorphic rocks produced in distinct facies, including high-, low-, and intermediate-grade rocks

c. it is possible to find a variety of metamorphic rocks produced in distinct facies, including high, low, and intermediate grade rocks

The mineral assemblage within metamorphic rock is : . a..always identical to that found within the protolith b..dependent only on the mineral assemblage of the protolith c..dependent only on the temperature and pressure of formation d..dependent on both the mineral content of the protolith and the temperature and pressure of formation

d. dependent on both the mineral content of the protolith and the temperature and pressure of formation

In the formation of gneiss from granite, the distinctive compositional bands form due to : . a..crystals migrating within the rock b..crystals dissolving, and atoms and ions migrating and reorganizing as new crystals c..crystals melting, with new crystals solidifying in color bands d..the bizarre and seemingly unknowable nature of the blueschist metamorphic facies

b. crystals dissolving, and atoms and ions migrating and reorganizing as new crystals

As compared to the amphibolite metamorphic facies, the greenschist facies : . a..consists of lower-grade rocks b..consists of higher-grade rocks c..is an identical temperature and pressure regime; greenschists and amphibolites bear different mineral assemblages only because of differences in protolith chemistry

a. consists of lower grade rocks

. Thermal (contact) metamorphism occurs : . a..in areas surrounding igneous intrusions b..only where gneiss is in contact with schist c..as consequence of the sinking of a broad region to great depth d..only at the surface, where rock is in contact with the atmosphere

a. only where gneiss is in contact with schist

Dynamothermal metamorphism occurs when : . a..rock becomes buried deeply during continental collision and mountain building b..regression of the sea leads to erosion of sedimentary cover atop a body of rock c..the upper surface of a body of rock develops a thick soil profile d..a pluton causes metamorphism in a small surrounding region

Which of the following processes cannot occur in the formation of metamorphic rock? a..realignment of minerals so that they develop a preferred orientation b..segregation of minerals into layers of different compositions c..solid-state rearrangement of atoms or ions to create a new assemblage of minerals d..complete remelting of the rock, followed by solidification to form a new rock

d. complete remelting of the rock, followed by solidification to form a new rock

Metamorphism, in broadest terms, involves : . a..the settling of crystals within a melt as it cools b..the sorting of grains by size, as is accomplished by rivers and beach waves c..cementation of loose grains and precipitation of new minerals into pore spaces d..changes in mineralogy and texture in response to heat and stress